Mon·Feb 3, 2020Monday·February 3, 2020

1. 01*

   Constraining the destruction rate of ${}^{40}$K in stellar nucleosynthesis through the study of the ${}^{40}$Ar(p,n)${}^{40}$K reaction

   P. Gastis · G. Perdikakis🇺🇸 · J. Dissanayake🇺🇸 · P. Tsintari · I. Sultana🇺🇸 · C.R. Brune🇺🇸 · T.N. Massey🇺🇸 · Z. Meisel🇺🇸 · A.V. Voinov🇺🇸 · K. Brandenburg🇲🇽 · T. Danley🇺🇸 · R. Giri🇺🇸 and 4 other authors

   40K plays a significant role in the radiogenic heating of earth-like exoplanets, which can affect the development of a habitable environment on their surfaces. The initial amount of 40K in the interior of these planets depends on the composition of the interstellar clouds from which they formed. Within this context, nuclear reactions that regulate the production of 40K during stellar evolution can play a critical role. In this study, we constrain for the first time the astrophysical reaction rate of 40K(n,p)40Ar, which is responsible for the destruction of 40K during stellar nucleosynthesis. We performed differential cross-section measurements on the 40Ar(p,n)40K reaction, for six energies in the center-of-mass between 3.2 and 4.0 MeV and various angles between 0-deg and 135-deg. The experiment took place at the Edwards Accelerator Laboratory at Ohio University using the beam swinger target location and a standard neutron time-of-flight technique. The total and partial cross-sections varied with energy due to the contribution from isobaric analog states and Ericson type fluctuations. The energy-averaged neutron angular distributions were symmetrical relative to 90-deg and consistent with the theoretical predictions of the statistical model. Based on the experimental data, local transmission coefficients were extracted and were used to calculate the astrophysical reaction rates of 40Ar(p,n)40K and 40K(n,p)40Ar reactions. Our results support that the destruction rate of 40K in massive stars via the 40K(n,p)40Ar reaction is larger compared to previous estimates. This result directly affects the predicted stellar yields of 40K from nucleosynthesis, which is a critical input parameter for the galactic chemical evolution models that are currently employed for the study of significant properties of exoplanets.

   nucl-exPRC(2020)·3 citations
2. 02*

   Beta decay of molecular tritium

   Y.-T. Lin🇺🇸 · T. H. Burritt🇺🇸 · C. Claessens🇩🇪 · G. Holman🇺🇸 · M. Kallander🇺🇸 · E. Machado🇺🇸 · L. I. Minter🇺🇸 · R. Ostertag🇩🇪 · D. S. Parno🇺🇸 · J. Pedersen🇺🇸 · D. A. Peterson🇺🇸 · R. G. H. Robertson🇺🇸 and 3 other authors

   The beta decay of tritium in the form of molecular TT is the basis of sensitive experiments to measure neutrino mass. The final-state electronic, vibrational, and rotational excitations modify the beta spectrum significantly, and are obtained from theory. We report measurements of the branching ratios to specific ionization states for the isotopolog HT. Two earlier, concordant measurements gave branching ratios of HT to the bound HHe${}^{+}$ ion of 89.5% and 93.2%, in sharp disagreement with the theoretical prediction of 55-57%, raising concerns about the theory's reliability in neutrino mass experiments. Our result, 56.5(6)%, is compatible with the theoretical expectation and disagrees strongly with the previous measurements.

   nucl-exPRL(2020)·16 citations
3. 03*

   Two-Pion Intensity Interferometry in Au + Au @ 1.23$A$ GeV

   Robert Greifenhagen (for the HADES collaboration)🇩🇪

   High-statistics ${\pi }^{-}{\pi }^{-}$ HBT data for non-central Au + Au collisions at 1.23$A$ GeV, measured with HADES at SIS18/GSI, are presented. The three-dimensional emission source is studied in dependence on pair transverse momentum and centrality. A tilt of the source relative to the beam axis is observed. The spatial extension and the tilt magnitude of the source decrease with transverse momentum. The spatial extension decreases and the tilt magnitude increases going from central to peripheral collisions. The derived eccentricity perpendicular to the beam axis fits well to the initial nucleonic overlap region at high transverse momentum.

   nucl-exNPA(2021)·1 citation
4. 04*

   Studying QGP with flow: A theory overview

   Chun Shen🇺🇸

   I review recent developments in the phenomenological study of the quark-gluon plasma (QGP) transport properties based on a personal selection of results that were presented at Quark Matter 2019. The constraints on the temperature dependence of QGP shear and bulk viscosity are summarized. I discuss new theory advancements towards more realistic 3D dynamical simulations of heavy-ion collisions at finite baryon density. The challenges and opportunities of applying hydrodynamics to small collision systems are highlighted.

   ↳ nucl-thhep-phnucl-exNPA(2021)·50 citations
5. 05*

   Quarkonium measurements in nucleus-nucleus collisions with ALICE

   Xiaozhi Bai (on behalf of the ALICE Collaboration)🇨🇳

   Heavy quarks are produced in the early stages of nucleus-nucleus collisions and can therefore provide important insight into the Quark-Gluon Plasma (QGP). Quarkonia are proposed as crucial probes to study the QGP. The extent of the medium modification for heavy-quark quarkonium production in heavy-ion collisions is measured in terms of a nuclear modification factor $R_{\mathrm{AA}}$, defined as the quarkonium yield in heavy-ion collisions divided by the relative quarkonium cross section in pp collisions scaled by the nuclear overlap function. A possible path-length dependent quarkonium dissociation, as well as a contribution of (re-)generation of quarkonia from heavy quarks in the medium, would lead to an azimuthal anisotropy of quarkonium production relative to the reaction plane. In this contribution, the recent ALICE measurements of quarkonium in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV will be discussed for both mid- and forward rapidity. The dependence of $R_{\mathrm{AA}}$ on centrality and $p_{\mathrm{T}}$ for J/$\psi$, ${\rm Y}$(1S), ${\rm Y}$(2S), as well as the J/$\psi$ elliptic flow $v_2$ will be shown. The experimental data and the current theoretical model calculations will be also discussed.

   ↳ hep-exnucl-exNPA(2021)·15 citations
6. 06*

   Measurement of the permanent electric dipole moment of the neutron

   C. Abel🇬🇧 · S. Afach🇨🇭 · N. J. Ayres🇬🇧 · C. A. Baker🇬🇧 · G. Ban🇫🇷 · G. Bison🇨🇭 · K. Bodek🇵🇱 · V. Bondar🇨🇭 · M. Burghoff🇩🇪 · E. Chanel🇨🇭 · Z. Chowdhuri🇨🇭 · P.-J. Chiu🇨🇭 and 72 other authors

   We present the result of an experiment to measure the electric dipole moment (EDM) of the neutron at the Paul Scherrer Institute using Ramsey's method of separated oscillating magnetic fields with ultracold neutrons (UCN). Our measurement stands in the long history of EDM experiments probing physics violating time reversal invariance. The salient features of this experiment were the use of a Hg-199 co-magnetometer and an array of optically pumped cesium vapor magnetometers to cancel and correct for magnetic field changes. The statistical analysis was performed on blinded datasets by two separate groups while the estimation of systematic effects profited from an unprecedented knowledge of the magnetic field. The measured value of the neutron EDM is $d_{\mathrm{n}}=(0.0\pm 1.1_{\mathrm{stat}}\pm 0.2_{\mathrm{sys}})\times 10^{-26}e\mathrm{cm}$.

   ↳ hep-exnucl-exphysics.ins-detPRL(2020)·1089 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.